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Hot water from cold pipes, plumbers are stumped

14K views 75 replies 17 participants last post by  karin els 
#1 ·
The problem
When faucets in our house are first used, you get a long wave of hot water from the cold water side. After a while, maybe 1-2 minutes, the water will finally get cold again. And when I say "hot" I mean too hot to touch. Things used to work fine, so this isn't a fundamental screwup in the plumbing.

The plumbing
I have a two-story home with recirculating hot water (dedicated return pipes). The water heater (WH) is in the garage, and was replaced about three years ago. It's a Kenmore 75 gallon unit, and I think our problems started sometime after the WH replacement. Originally, the hot water return went to the recirculating pump, and then into a T-connector on the WH cold input. The first fix attempt (which was well after the new WH was installed) replaced the recirc pump with a Grundfos UP10-16BU ATLC (which has in internal check valve), and replumbed the water return line to enter the WH through the lower drain spigot. This seemed to help a little with our problem, but didn't fix it.

What I've done to diagnose
For all faucets or other appliances that connect to the hot water and have accessible cut-off valves, I tried turning off the hot water to see if that helped. None made any difference. We still have about six bath and shower valves where the pumping is in the wall so I can't turn off the hot side manually. I believe all of them are Delta brand. I also tried unplugging the recirculating pump: this effectively reversed the problem: we'd no longer get hot water from the cold taps, but then we'd get cold from the hot side for a couple minutes. Basically, what you'd expect without recirculation. I've had two plumbers come check out my system. The first "checked" all of my in-wall faucets and declared them to be fine, replaced my hot water recirculating pump, and rerouted the return water line. That didn't fix the problem. The second plumber wanted to install a check valve in series with the pump, but since the pump has an internal check valve I wouldn't let him. I became suspicious that we were getting convection (thermal) mixing, so I had plumber #2 put a 8-inch vertical rise and fall in the cold water input to the WH (like an upside-down sink trap; I think this is called a heat trap). But that made no difference.

Both plumbers suggested putting in a cold water check valve to prevent backflow from the WH, but I'm reluctant to do this. For one thing, I believe CA plumbing code requires that I also install a thermal expansion tank, which is extra cost, annoyance, and potential maintenance hassle. But more importantly, everything used to work fine without a cold water check valve. There should be no way for hot water to be pumped through the cold water system, unless I have some crossover connection between my hot and cold lines.

Ideas? Can Delta mixer valves leak from hot-to-cold without water coming out of the fixture?
 
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#20 · (Edited)
Not approved in Ohio anymore we had a scald burn occur with lawsuit.

"From my original posting: "I also tried unplugging the recirculating pump: this effectively reversed the problem: we'd no longer get hot water from the cold taps, but then we'd get cold from the hot side for a couple minutes. Basically, what you'd expect without recirculation."

This is telling me you need check valves, repipe it correctly and install a swing check before the pump on the return and one above your tie in on the cold inlet. I bet your headache will go away...
 
#21 ·
Not approved in Ohio anymore we had a scald burn occur with lawsuit.
Wow. Do you happen to have a reference to that lawsuit?

"From my original posting: "I also tried unplugging the recirculating pump: this effectively reversed the problem: we'd no longer get hot water from the cold taps, but then we'd get cold from the hot side for a couple minutes. Basically, what you'd expect without recirculation."

This is telling me you need check valves, repipe it correctly and install a swing check before the pump on the return and one above your tie in on the cold inlet. I bet your headache will go away...
Can you explain how the proposed check valves will solve my problem?

The check valve "before the pump" should be redundant with the check valve in the pump.

When you say "above your tie in on the cold inlet," I assume you mean on the cold input from the street, before the tie-in with the (replumbed) hot water return, correct? Note that the original setup, which worked fine for years abut then developed this same hot-water-from-cold-pipe problem, was plumbed the way you suggest, minus the cold water check valve. Replacing the recirculating pump and replumbing the hot water return to the WH drain pipe was plumber #1's attempt at fixing my problem. I'll also add that the $700 I spent on that "fix", despite it not really making sense to me, is why I'm so skeptical of proposed solutions now.

Note also that California plumbing code and my water heater's warranty both require me to install a hot water expansion tank if I put a check valve on my cold water input, and I'm trying to avoid doing that. Since the system originally worked fine for many years without such a check valve, I'm baffled why I need one now to fix it.

Maybe I'm being simplistic, but it seems to me that if hot water is getting into my cold pipes, the cold water it's replacing has to take the hot water's place. That is, there must be a loop that includes my cold water pipes and my water heater. In theory, this loop could flow either direction (WH->hot pipes->mystery connection->cold pipes->WH, or WH->cold pipes->mystery connection->hot pipes->WH). A cold water check valve only helps with one of those cases, and furthermore it seems to be avoid the "real" problem if the "mystery connection".

The only alternative to a real loop that I can think of is convection within a pipe. But I believe modern water heaters all have heat traps to avoid this, plus I had plumber #2 extend the hot and cold connections on top of the WH so they'd have a small vertical rise and fall, which I understand is an old-school heat trap. That didn't fix the problem, either.

-Seabeast
 
#64 ·
Just for giggles sea beast could you turn off the cold to the hot water tank. Turn off the recirculation line hope it has a valve. Then open up the KS faucet hot only and see if it has any pressure after 3 or 4 minutes. It will take time to bleed off your expansion tank. Also turn your pump off on the recirculation line.

If the hot still has pressure then we are dealing with a cross connection and a Delta can do this. And your washer machine can also.
 
#73 ·
No, Ghostmaker gets the prize. The shower valves were a suspect before I even posted here, as mentioned in post #1. That's why I had the first plumber check them.

Ghostmaker was the first to suggest an experiment that actually identified the culprit.

Ever see those signs in car shops that say something like "Parts $20, labor $20, knowing which part to replace $500." That was pretty much my situation.
 
#8 ·
I suspect one or more shower cartridges are the problem
That's what I suspected, too, though I contacted Delta and they insist that if their cartridges leak, this will be evident by water coming out of the fixture. Maybe that's just marketing talking, but I had previously read similar assertions (it can't happen with Delta cartridges, only with certain other brands).

Still, this seems the like the best candidate solution. The problem is that my house has five of these cartridges, and at $40 each it's pretty pricey to replace them all speculatively, and really time-consuming to replace them one-by-one (each time I have to drain the water lines, replace the cartridge, turn water back on, and wait several hours to see if the problem went away).

-Seabeast
 
#3 ·
Where are you?

The last time we saw this problem,the member was from southern California and the pipes were run through a hot attic----and were heated up there--no plumbing problems at all---
 
#7 ·
I'm in Northern CA. I saw the thread you're referencing during my pre-posting searches, but I'm pretty confident that's not my situation. Evidence in support of my position:
  • We get the problem first thing in the morning, after the house has cooled down.
  • We get the problem year round, even on overcast or cold days.
  • The water is really, really hot, not just warm like the prior poster's.

-Seabeast
 
#4 ·
Since turning off the pump stops the issue it can be concluded that there is at least one fixture passing water. Any one handled device that mixes hot & cold could be at fault.

I would get up in the early in the morning before any water is used and feel the fixtures for warmth. The offending device(s) will be warm while the ones that are OK will be ambient.
 
#9 ·
This is a good idea. I tried it this morning, but all of the handles felt room temperature to me.

I have an infrared thermometer hidden somewhere in my house (ahem!), and once I find it I'll try the experiment again using more precise readings. I'd really love to pinpoint one (or two) suspect fixtures.

-Seabeast
 
#6 ·
The cold water pipe going into your hot water heater ---- if you hold the pipe 3 feet from the water heater, is it hot or cold?
Unfortunately, there are only about two feet of pipe before it enters the wall, but it feels pretty consistently warm along those two feet.

On page 5 of this manual http://www.pexuniverse.com/docs/pdf/Grundfos-Comfort-Series-Installation-Manual.pdf they specify allowed and not-allowed orientations for the pump. Is your pump mounted in an allowed orientation?
Yes, it's mounted with the pipe vertical, flowing down, and the motor extending horizontally from the wall, just like cover illustration.

-Seabeast
 
#10 ·
#15 ·
Last night I checked the kitchen faucet. The cold water temp started at around 78, then after 10-15 seconds rose to 110, held that temperature for another 10 seconds or so, and then slowly dropped back to 78. Interestingly, when I then turned the handle to HOT, the maximum I measured was also 110. This was surprising, since I have my WH set to "B", which the manual claims is 140F. I don't expect 140 at the fixture, but with HW recirculating I would expect to get above 120F at least. To be fair, my wife had recently been doing dishes in the sink, so some HW had been used, but surely not enough to make a dent in my 75 gallon WH.

Later, I repeated the test at an upstairs bathroom and got similar readings for both hot and cold.

This morning I did the test again. This time the HOT side got a little above 120F (hard to read precisely on that tiny thermometer dial), but the cold side still peaked at around 110.

On the topic of WH temperature, the last plumber I consulted on this problem was alarmed that I had my WH temperature set to a little above "C". He rattled off a long list of disasters this would surely cause, including hot water from my cold taps, melted washers, blurred vision, flatulence, etc. To humor him, I dropped the temperature down to "A" for a night to see if that would solve my hot-in-the-cold water problem, which of course it didn't. But then I did some research on what A, B, and C meant, and decided to go with "B". Supposedly on my Kenmore WH, A=130F, B=140F, and C=150F. The question buried in this is "what are the odds that 'B' really corresponds to 140, and if they're not good, what's the recommended method of determining the actual WH temperature?"
 
#14 ·
The handles may be too insulated from the fixture by plastic cartridge parts. Check a metallic area or better yet the connection pipes on sink faucets and the cold side of the valve body on showers. (requires removal of handle and escutcheon plate)
 
#18 ·
For all of the sink faucets, I previously experimented with turning off their hot water connection entirely for a day, so I believe all of the faucets are blameless. That just leaves the bath/shower mixer valves under a cloud of suspicion. I'll try removing the base plates to see if that gives me access to any cutoff valves or at least a way to directly measure the temperatures of the "cold" supply pipes.

Other than the sinks, baths, washing machine, and dishwasher, are there any other places in house plumbing where cold and hot water come together? A Delta representative called me yesterday and assured me it's impossible to get this kind of mixing in their mixer cartridges without water coming out of the fixture. Is it possible a builder might have installed some sort of standalone hot-cold pressure equalizer somewhere in the plumbing? Is that even a thing?

-Seabeast
 
#16 ·
I have never seen a delta cartridge cross over. I do not think it is possible with the way they are constructed. They use a cup spring arrangement on a stainless steel plate that seals the hot and cold. No o rings are involved with the hot and cold water itself. The only O rings are sealing the entire cartridge from leaking.

If a cup spring should leak it will exit the faucet.

Only Moen single handle may cause cross over.
 
#17 · (Edited)
Try the obvious and unplug your return pump and see how things work.
By the way a return into the lower tank is not good plumbing it causes stacking of temperatures in the tank and overheated water because it will fire the burner more often

I'm thinking you have a bad check on the pump or some garbage is in it preventing it from closing tight.
 
#19 ·
Try the obvious and unplug your return pump and see how things work.
From my original posting: "I also tried unplugging the recirculating pump: this effectively reversed the problem: we'd no longer get hot water from the cold taps, but then we'd get cold from the hot side for a couple minutes. Basically, what you'd expect without recirculation."

By the way a return into the lower tank is not good plumbing it causes stacking of temperatures in the tank and overheated water because it will fire the burner more often
Interesting. That does make sense, though I'll note that the lower tank method seems to be widely recommended:

-Seabeast
 
#24 ·
That was my thought as well.

I think I would go to each faucet...run the cold until it's cold water....and then shut off the water under the sink using the shut off valves.

At this point, the cold water line should be full of cold water.

Wait awhile....then take turns turning on sinks....depending on where the leak is (shower?), the sink closest to the leaking shower should be hot first.

Or....install test plugs in the rough in's in the shower.
 
#23 · (Edited)
Good point E plumber.
Seabeast sometimes you need to see the tree in the forest. Your original set up was this.

" Originally, the hot water return went to the recirculating pump, and then into a T-connector on the WH cold input. The first fix attempt (which was well after the new WH was installed) replaced the recirc pump with a Grundfos UP10-16BU ATLC (which has in internal check valve), and replumbed the water return line to enter the WH through the lower drain spigot. This seemed to help a little with our problem, but didn't fix it."

Now before you replaced your hot water tank did your system work properly? If your answer is yes

Then I submit to you that when they replaced your hot water tank debris in your water line prevented your check valve from closing.

Your plumber opted for the grand fix and repiped your system and replaced your pump. When he did all that wonderful expensive work did he leave installed the old check valves on your cold water and return line?

As an engineer in what ever field you are in KISS is still the rule of the land.

Have a great day.
 
#25 ·
Good point E plumber.
Seabeast sometimes you need to see the tree in the forest. Your original set up was this.

"Originally, the hot water return went to the recirculating pump, and then into a T-connector on the WH cold input. The first fix attempt (which was well after the new WH was installed) replaced the recirc pump with a Grundfos UP10-16BU ATLC (which has in internal check valve), and replumbed the water return line to enter the WH through the lower drain spigot. This seemed to help a little with our problem, but didn't fix it."

Now before you replaced your hot water tank did your system work properly? If your answer is yes

Then I submit to you that when they replaced your hot water tank debris in your water line prevented your check valve from closing.

Your plumber opted for the grand fix and repiped your system and replaced your pump. When he did all that wonderful expensive work did he leave installed the old check valves on your cold water and return line?
Notice that there is no mention of a cold water check valve in my description of my original setup.

Maybe I worded it strangely, but what I was trying to explain in the prior posts is that, as far as I can tell, I have never had a cold water check valve in my system. Yet the system used to work.

I don't know if the original (working) setup had any check valves at all, though I suspect it probably had one on the recirculating return line. It definitely has one on that line now, because it's built into the new recirculating pump.

As an engineer in what ever field you are in KISS is still the rule of the land.
KISS is a fine principle. And not that it matters, but I'm an electrical engineer. I mentioned being an engineer not to assert any sort of authority, but to help explain why I'm asking so many questions rather than just accepting proposed solutions. Engineers tend to need to understand how things work.

-Seabeast
 
#29 ·
Theoretically, if the water heater thermostatic element is set at 120 degrees Fahrenheit, the burner would come on when the temperature at the thermostat reaches about 105 degrees Fahrenheit. The burner stays on until the water around the thermostat element near the bottom of the heater reaches about 135 degrees Fahrenheit (about 30 degrees higher than when the burner came on and 15 degrees above the theoretical set point of the thermostat).
Most people don't realize that the maximum temperature limit test of the ANSI Z21.10.1 Gas Water Heater Standard allows the outlet water temperature of the water heater to rise 30 F above the thermostat setting. This provision in the standard accounts for the phenomenon known as "stacking" or "thermal layering". The hot water is less dense and rises to the top of the hot water tank. The cooler water drops to the bottom of the tank. Stacking or layering occurs when hot water rises to the top of the heater due to recurring short duration heating cycles caused by a frequent number of small quantity hot water uses. This phenomenon can occur in any type of storage water heater and generally is more significant in vertical heaters.
At the top of a water heater that is theoretically set for 120 F to prevent scalding, the temperatures can easily reach 150 to 165 degrees Fahrenheit. These extremely high temperatures will cause third degrees burns and severe scald injuries in an instant upon contact with the skin. This is why I highly recommend installing the proper type of an ASSE 1017 thermostatic mixing valve on the outlet piping of a water heater to limit the hot water distribution temperatures to a maximum safe delivery temperature of 120 F. If high temperature hot water uses are required in a building, I recommend installing an ASSE 1070 thermostatic mixing valve on the local branch piping serving a fixture or group of fixtures. The mixing valve can then reduce the hot water temperature to a safe temperature.
 
#30 · (Edited)
Seabeast again, what is the temperature of the water coming out at the fixtures, when you turn on the Cold water faucet? You have never stated that temp, just keep going on that the water is hot, now you are pulling stuff up about something irrelevant.

Hot to some may not be hot to others, and it helps to know what is the physical measured temp. that you are getting, when you turn on the Cold water at various fixtures in the home, this includes the outside water spigot.

BTW Ghost, a little heavy on the 411. Goes way past what the OP is trying to figure out, and still cannot figure out how that fits in. Me thinks that we need to go back to the basic problem, which I am going with either the OP lives where they may have a heat wave going on for that period, which caused incoming water temps to be higher than average, like we did last year all across the country, or that they have a messed up plumbing system with that recirc, and that is what is causing the issue, not this all over the board reasoning of what it could be, but actually may not.
 
#33 ·
Seabeast again, what is the temperature of the water coming out at the fixtures, when you turn on the Cold water faucet? You have never stated that temp, just keep going on that the water is hot, now you are pulling stuff up about something irrelevant.

Hot to some may not be hot to others, and it helps to know what is the physical measured temp. that you are getting, when you turn on the Cold water at various fixtures in the home, this includes the outside water spigot.
I did previously reply to your request for temps, way back in post #15 of the thread: http://www.diychatroom.com/f7/hot-water-cold-pipes-plumbers-stumped-184533/#post1223831

But I'll give the short version again for convenience: 110 degrees F.

I live in San Jose, CA 95138. If you check a weather website, you'll find that we've been having very moderate days in the upper 70s, and cool nights in the mid 50s: http://www.wunderground.com/history/airport/KSJC/2013/8/1/MonthlyHistory.html#calendar

I contend that after cooling overnight in below 60F darkness, it's not normal to have 110F water coming from your cold pipes in the morning. Furthermore, the problem has been going on for at least a year, including the cooler winter months. Agreed?

BTW Ghost, a little heavy on the 411. Goes way past what the OP is trying to figure out, and still cannot figure out how that fits in. Me thinks that we need to go back to the basic problem, which I am going with either the OP lives where they may have a heat wave going on for that period, which caused incoming water temps to be higher than average, like we did last year all across the country, or that they have a messed up plumbing system with that recirc, and that is what is causing the issue, not this all over the board reasoning of what it could be, but actually may not.
Actually, I appreciate the 411, and in fact he's convinced me that when I do end up hiring a plumber to add check valves or whatever, I'll also see about having a thermostatic mixer installed. I like keeping the WH pretty hot, but 120F is all we need at the handles. I hadn't realized the temperatures varied so wildly in a normally-functioning WH.

That said, my priority is still resolving my original problem.

-Seabeast
 
#31 ·
gregzoll said:
Ghostmaker, again, what is the temperature of the water coming out at the fixtures, when you turn on the Cold water faucet? You have never stated that temp, just keep going on that the water is hot, now you are pulling stuff up about something irrelevant.

Hot to some may not be hot to others, and it helps to know what is the physical measured temp. that you are getting, when you turn on the Cold water at various fixtures in the home, this includes the outside water spigot.
How would Ghost know the temps?

Sent from my iPhone using DIY Forum. Watch out for spell check
 
#34 ·
One thing is clear. The recirc loop is compromised. In my experience this has always been traced to the dish sprayer in the kitchen. (institutional) These are connected to both hot and cold water and left turned on while the trigger on the spray nozzle is used periodically to release the water. There are in line back flow preventers installed that arrest the flow of water through the fixture in either direction. When these fail the fixture becomes a flow through branch that will feed other fixtures when they are opened. This will happen without a pump involved too.

Somewhere in your homes plumbing there is a bridge. You have stated that all worked well at one point then abruptly went south. Something changed to cause this and your memory of any new equipment or removal of old equipment is going to take you to the culprit. Something like a laundry tub with a hose and a hose end sprayer attached to it, if left on will appear harmless enough but the water will flow in the pipes. It has to be somewhere.
 
#39 ·
The only sprayer in the kitchen is in the main faucet head, and it doesn't have its own on/off valve. And I tried turning off the hot water input to the kitchen faucet, but the problem persisted.

We don't have a Jacuzzi, hot tub, laundry tub with hose sprayer, or any other water connections I can think of that I haven't listed here already.

I suppose it's possible I have two cross-connects, and thus my systematic one-by-one disabling of the hot water to each faucet might not have stopped the problem.

This weekend I intend to remove the base plates around the in-wall shower valves, and then take my IR thermometer and try to find one (or more!!) valves with unusually warm cold-water connections. That seems like the most direct diagnostic method suggested here so far.

I'm also going to try taking a look at my neighbor's hot water setups, just to make sure I'm properly remembering the original state of mine.

Thanks everyone for sticking with me on this issue. At this point I'm not sure if my wife is more annoyed by the hot water or by my obsession with resolving it.

-Brett
 
#35 · (Edited)
A little buried back there seabeast. You have issues with a crossover or that recirc system. Is there a valve somewhere that is open before or after the pump, that shouldn't? Personally I would take it out of the loop, get rid of it, if it is tempering water that high, there are issues with the way it was designed.

Do not know if this was inquired about before, what is the longest single pipe run from the water heater to the last fixture in the house? How old is the water heater?

This is the tempering valve we had installed http://www.amazon.com/gp/product/B000BQMKCY/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1 My plumber placed two gate valves behind it, so that if we need to remove to clean any crud out of the two cups inside, we can shut it off. I have to use the hot water Ball valve to adjust the hot water, due to using the adjustment on the fixture valve itself, does not do the job properly. Only bad thing I can state about it, is that the water pressure is lower to the toilet that it goes to, not at the full psi that we get incoming. The wife is happy, that the toilet does not sweat. There are others out there, that are built different than this one, so look around, since the one I posted is just an example.
 
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